Question: We have 2 sorted arrays and we want to combine them into a single sorted array.
Input: arr1[] = 1, 4, 6, 8, 13, 25 || arr2[] = 2, 7, 10, 11, 19, 50
Output: 1, 2, 4, 6, 7, 8, 10, 11, 13, 19, 50
最简单的方法之一就是把两个数组复制到一个新的数组中，对这个新的数组进行排序。但这样就不能利用原来的两个数组已经排好序这个条件了。
我们需要一个不一样的方法。下面是可行方法之一：
- 为两个数组初始化两个变量作为索引。
- 假设i指向arr1[]，j指向arr2[]。
- 比较arr1[i]，arr2[j]，哪个小就将那个复制进新的数组，并增加相应的系数。
- 重复上述步骤直到i和j都到达数组尾部。
相应的算法实现：
#include<stdio.h> //a function to merge two arrays
//array1 is of size 'l'
//array2 is of size 'm'
//array3 is of size n=l+m
void merge(int arr1[], int arr2[], int arr3[], int l, int m, int n)
{
//3 counters to point at indexes of 3 arrays
int i,j,k;
i=j=k=0; //loop until the array 1 and array 2 are within bounds
while(i<l && j<m)
{
//find the smaller element among the two
//and increase the counter
if(arr1[i] < arr2[j])
{
arr3[k] = arr1[i]; //increment counter of 1st array
i++;
}
else
{
arr3[k] = arr2[j]; //increment counter of second array
j++;
} //increase the counter of the final array
k++;
} //now fill the remaining elements as it is since they are
//already sorted
while(i<l)
{
arr3[k] = arr1[i];
i++;
k++;
}
while(j<m)
{
arr3[k] = arr2[j];
j++;
k++;
}
} //driver program to test the above function
int main(void)
{
int arr1[5] = {1, 5, 9, 11, 15};
int arr2[5] = {2, 4, 13, 99, 100}; int arr3[10] = {0}; merge(arr1, arr2, arr3, 5, 5, 10); int i=0;
for(i=0;i<10;i++)
printf("%d ",arr3[i]); return 0;
}